Synergistic effect of chemical crosslinking and addition of graphene-oxide in Chitosan—Hydrogels, films, and drug delivery

We investigate the synergistic effect of chemical crosslinking by Glutaraldehyde (GA) and physical crosslinking induced by Graphene Oxide (GO) nanosheets addition on Chitosan (CH) to enhance the mechanical strength of CH hydrogels and their films. An increase in the [GA] and GO loading in CH hydrogels increase the G' (Storage Modulus) and τ<inf>y</inf>(Yield Stress) values. The G' of 0.5 wt% GO incorporated 53 mM [GA] crosslinked CH hydrogel is 7.2 times greater than the 53 mM [GA] crosslinked CH hydrogel. The morphology studies by FESEM indicate that the porosity of CH-GA and CH-GO-GA hydrogels improves with an increase in the [GA] and GO loading. The CH-GO (0.1 wt%)-GA(35.3 mM) nanocomposite hydrogel film displays a higher Young's modulus than the pristine CH film by more than 20 times. Drug delivery studies carried on the tetracycline hydrochloride (TH) loaded films show a pH-responsive behavior where the drug elusion is higher at pH 4 than pH 7.4. Sustained drug delivery is observed in 0.1 wt% GO-loaded CH film crosslinked with [GA] = 35 mM. The GA crosslinking and GO nanosheets incorporation play a prominent role in reducing the burst release from the CH films.